This invention relates generally to synthetic blood, and more particularly to an improved blood substitute offering improvements in oxygen carrying capacity and stability, as well as lessened risk of anaphylactoid reaction.
The facile transport of oxygen through Teflon (polyperfluoroethylene) membrane has been well known for many years. The realization of the compatibility of perfluorocarbons with oxygen led to a series of research efforts which subsequently arrived at the utilization of perfluorochemicals as oxygen carriers in a new generation of blood substitutes.
Initial work by Leland Clark of Cincinnati Childrens Hospital, Robert Geyer of Harvard and Henry Sloviter of the University of Pennsylvania, continued and extended by Naito and co-workers, led to a preparation (Fluosol DA 20%) produced for clinical testing by Green Cross of Osaka, Japan. Fluosol DA functioned as an oxygen carrier in animal experiments and showed considerable promise for human use.
However, Fluosol DA* had several significant drawbacks. First, the emulsion of fluorochemical droplets in an aqueous phase was inherently unstable, both thermodynamically and kinetically, necessitating storage of the emulsion in the frozen state. This instability also entailed a laborious and time consuming blending of the emulsion with other accessory solutions immediately before use. As second major problem with Fluosol DA was the FNT * perfluorodecalin necessity of maintaining the patient on 70 to 100% oxygen to ensure sufficient oxygen supply and exchange in the tissues. Finally, limited clinical experience with Fluosol DA showed an incidence of transfusion reactions and, in order to avoid this problem, led to the pretreatment of patients with steroids in the event a small test dose indicated sensitivity; this type of sensitivity appeared in 3% or less of all cases.